1. Field of the Invention
The present disclosure relates to density control techniques in image forming apparatuses.
2. Description of the Related Art
Image forming apparatuses that use electrophotographic systems require stable densities and tones in output images. To that end, U.S. Pat. No. 5,752,126 and U.S. Pat. No. 5,583,644 disclose configurations that stabilize the quality of an image by forming a test pattern on an image carrier and adjust image forming conditions, generate a tone correction table, and so on by reading the density of the formed test pattern using a sensor.
When creating a tone correction table, correction values for densities not formed by the test pattern are obtained by interpolating results of measuring the densities formed by the test pattern. However, pixel values in the image data provided to the image forming apparatus and the densities actually formed by those pixel values are not in a linear relationship, and error appears particularly in low-density and high-density regions where the degree of non-linearity is more marked. Although increasing the number of densities formed by the test pattern is conceivable as a way to solve this problem, doing so increases the time required for tone control and drastically reduces productivity.